The present invention generally relates to a data processing apparatus, a data processing method, a data reading apparatus, and a data recording apparatus. More particularly, the present invention relates to a data processing apparatus, a data processing method, a data reading apparatus, and a data recording apparatus incorporated in a watermark embedding system for embedding digital watermark information in information signals for the purpose of copyright protection.
In recent years, as digital content delivered over the Internet or contained on digital video discs (DVDs) has become widely available, there are problems with copyright violation due to unauthorized reproduction of video/image/audio data content.
To address such copyright violation problems, one approach has been proposed in which additional information for copyright protection, such as copy control information, is added to the video/image/audio content to prevent unauthorized reproduction of the content.
This additional copyright information is inserted in the content so that it becomes difficult to tamper with, falsify, or remove the copyright information, and unauthorized reproduction of the content can be effectively prevented.
One possible way to embed such additional information in the content is a digital watermarking technique. This technique allows additional information for copyright protection, such as copy control information, to be embedded as noise in perceptually less significant regions of video or music data, or in regions of the video or music data which are redundant. Specifically, for example, a spread-spectrum watermarking method is contemplated in which key patterns generated using random numbers or M-sequences are employed for addition or detection of additional information.
Additional information embedded in video or music data by this digital watermarking technique is difficult to remove as well as difficult to tamper with. Furthermore, if the video or music data is filtered or compressed, the embedded additional information can still be detected from the video or music data.
Superposing additional information on video data or the like according to the digital watermarking technique may thus provide an anti-tampering function to prevent unauthorized reproduction of the data.
However, conventional devices such as DVD (Digital Video Disc) players may encounter problems in that additional information such as copy control information which forms a watermark embedded in video data or the like is undetectable because the watermarking format is altered.
For example, additional copy control information may be a spread-spectrum watermark using random numbers and may be added to the video data as watermark information. In a DVD player for playing a DVD having the video data recorded thereon, once the video data read from the DVD is subjected to zooming for image enlargement, interpolation of pixels or horizontal lines of the image may occur. Thus, if the resultant spread-spectrum data is despread, the copy control information embedded therein would be undetectable.
Signal processing other than zooming, such as image rotation, inversion, cropping in which some portions of the image are cropped, or image shifting, which operations may change the number of pixels or lines, or their positions, or which may involve interpolation or decimation, would also cause problems in that the watermark information would be undetectable.